Automobile and other female fuse assemblies commonly comprise a two-piece assembly heretofore having a box-like housing and an all metal female one-piece fuse element secured therein. The metal female fuse element has a pair of spaced apart female terminals which are accessible from one end of the housing. The female terminals are closely encompassed by the housing walls. A fuse link unsupported between the ends thereof extends suspended between the extensions of the female terminals. The fuse link is spaced from the housing side walls which are closely spaced from the fuse link. A low fusing point metal is typically attached to the fuse link. The housing has slot-like openings at one end of the housing, and the female terminals are accessible from these slot-like openings where male blade-type terminals can be plugged into the female terminals. These male blade-type conductors typically extend from mounting panel or fuse block. This type of one-piece female fuse element and method of making the same are described in U.S. Pat. Nos. 4,570,147, 4,751,490, 4,958,426 and 4,344,060.
Automobile and other female fuse assemblies also have included an all metal female three-piece fuse element in place of a one-piece fuse element. As in the previously mentioned female fuses, the metal female fuse element has a pair of spaced apart female terminals which are accessible from one end of the housing. However, the female terminals can be created from typical male terminals by adding female sockets to the male terminals instead of forming the complete female fuse element from one piece. This structure and method of making the same are described in U.S. Pat. Nos. 4,672,352, and 4,869,972.
There are several constraints which exist when working with a one-piece female fuse construction. For example, the stiffness or resilience (spring qualities) of the fuse element material as well as the conductivity of the fuse element material both become important factors in determining the materials to be used. It is clear that the conductivity of the material is important due to principle that unnecessary resistance will reduce the amount of current flowing through the fuse. The resilience of the material is also important because the female engagement portion of the female fuse element must be durable and spring-like in order to continuously grip the male terminals on the terminal block in a snug manner. The resiliency is also a factor due to gravitational forces exerted on the fuse element when current heats up the fuse element (See U.S. Pat. No. 4,635,023). Other factors are involved, as well, in choosing the material to be used. Thus, at least both conductivity and resiliency are important factors. However, choosing a material to satisfy one factor will often not satisfy the other factor and trade-offs must be made with respect to such factors.
When a designer designs a proper construction for a three-piece fuse, the designer can choose materials for the fuse element which are different from the materials of the female sockets. Specifically, when a proper deign is chosen, the designer can choose a material for the fuse element which will allow for suitable conductivity, while at the same time the designer can choose a different material for the female sockets which will provide ample resilience to effect a snug fit between the fuse element, the sockets, and male terminals inserted therein. A snug fit will keep the resistance low (i.e. loss of current low) between the terminals of the fuse element and male terminals connected or linked thereto by the sockets. A snug fit only exists if there is no movement between the fuse element, the sockets, and male terminals inserted therein. These elements, snugly fit together, should also remain still, relative to their housing, to prevent the snug fit from being broken by any movement between these elements. If the fit between the fuse element, the sockets, and the male terminals inserted therein does not remain snug over time, the resistance therebetween, and the loss of current created therefrom, will be unsatisfactory for prolonged commercial use.
Specifically, although U.S. Pat. No. 4,869,972 (Hatagishi) discloses a three-piece female fuse configuration, this patent does not disclose a configuration that lends itself to a prolonged snug fit. The female sockets from this patent is only disclosed as being used for testing. In addition, if this configuration was placed in a commercial environment (i.e. onto a male fuse block within an automobile), small vibrations in the commercial environment would cause the fit between the fuse element, the sockets, and male terminals inserted therein to move about and loosen. No features are shown to lock or create a fit which can be completely snug. Without a snug fit, movement between these elements would cause a higher resistance within the fit, thereby causing a loss of current as well as unwanted heating of the fuse connections near the fuse block.
U.S. Pat. No. 4,672,352 also discloses a three-piece fuse assembly which includes a fuse element, tab insertion sockets (sockets), and a housing to house the same. The focus of the patent is that the fuse element can be replaced without replacing the sockets or housing. Thus, construction of the housing allows for the fuse element to be removed without removing the sockets. This construction also does not have any kind of firm fit of the sockets or fuse element within the housing unless a male terminal is inserted therein to force these elements outward from the male terminal. In addition, the fuse element in not secured to the socket in any way. The sockets are secured to the housing separate from the fuse element being secured to the housing. If the fuse terminal moves within the housing, not only will the fuse element move in relation to the housing, the fuse element will also move in relation to the sockets therein. Movement of the fuse element would also likely take place relative to the male terminal as well. Likewise, if the socket moves within the housing, the socket will not only move in relation to the housing, the socket will also move in relation to the fuse element. Movement of the socket will also likely take place relative to the male terminal as well. All of these possibilities of movement of the elements within the housing increases the probability of an increase of resistance and a loss of current.
The present invention is provided to solve these and other problems.